The present invention relates to the identification of a JOINTLESS gene from a tomato plant (genus Lycopersicon). More specifically, the invention relates to novel nucleic acid molecules isolated from a tomato plant, proteins encoded by such nucleic acid molecules, and antibodies raised against such proteins. The present invention is also directed to a nucleic acid homolog of a JOINTLESS gene and a method to identify a homolog.
The present invention relates to the JOINTLESS gene, a new MADS-box gene in a distinct phylogenetic group separate from those functioning in floral organs. A deletion in the JOINTLESS gene is likely responsible for the failure to activate the pathway for development of the pedicel abscission zone in jointless tomato plants (genus Lycopersicon). The invention further relates to the identification of novel nucleic acid molecules, or degenerate variants thereof, and polypeptides encoded by such nucleic acid molecules that suppress the formation of flower and fruit pedicel abscission zones in tomato.
The publications cited herein to clarify the background of the invention and in particular, materials cited to provide additional details regarding the practice of the invention, are incorporated herein by reference, and for convenience are cited in the following text.
Abscission is a universal and dynamic process occurring in the plant kingdom whereby fruit, flowers, and leaves are shed during both the normal course of development and in response to tissue damage and stress. Abscission occurs in plants at a morphologically distinct region called the abscission zone (AZ). Like some other members of the Solanaceae family such as potato, the AZ in the tomato is formed in the middle of the pedicel and is easily visualized as an indentation or xe2x80x9cjointxe2x80x9d consisting of five to ten tiers of unexpanded cells transversing the pedicel (Roberts et al., Planta 160: 159-163, 1984, the content of which is incorporated herein by reference in its entirety). Jointed plants shed flowers and fruit at the abscission zone while often retaining the distal parts of pedicels and calyxes.
Although much is known about the physiological process of abscission at fully developed AZ, the mechanism regulating the development of the AZ is not yet fully understood (reviewed by Sexton and Roberts, Ann Rev Plant Physiol 33: 133, 1982, the content of which is incorporated herein by reference in its entirety).
In tomato, the jointless (j) and jointless-2 (j2) mutations (L. Butler, J. Hered. 37: 25, 1936 and C. M. Rick, Am J Bot, 43: 687, 1956 respectively) completely suppress the formation of pedicel AZ. The jointless (j) and Jointless-2 (j2) mutations have been genetically mapped to chromosome 11 and chromosome 12 respectively (L. Butler, J Hered 37: 25, 1936; Rick and Yoder, Annu Rev Genet 22: 281, 1988 and Zhang et al., Theor Appl Genet, in press, respectively). Both simple recessive mutations, jointless also affects determinate growth: inflorescence meristems revert to vegetative growth after forming only one or two flowers, resulting in a xe2x80x9cleafyxe2x80x9d inflorescence phenotype (Rick and Sawant, Am Soc Hort Sci 66: 354, 1955 and Pnueli et al., Development 125: 1979, 1998). In addition to its biological significance in providing a means to study AZ development, jointless has agronomic value. Since there is no region on the pedicel at which the jointless plant can shed its flowers or fruit, unfertilized flowers shrivel and die on the pedicels and fruit remains on the plant until manually harvested. This latter property is useful in the tomato processing industry because the final product is a stemless tomato fruit, which aids in mechanical harvesting.
Accordingly, it has become increasingly important to identify and isolate the JOINTLESS gene to enable modification of flower and fruit abscission in plants. Additionally, the identification and isolation of the JOINTLESS gene in tomato will enable homologous genes in other plant species to be identified and isolated, especially in those species in which the creation of a jointless or abscission zone-free line would be economically advantageous such as cotton, oil rape seed and soybean.
The present invention relates to the isolation and identification of novel nucleic acid molecules, and degenerate variants thereof, and to the proteins encoded by such nucleic acid molecules which relate to the development and formation of flower and fruit pedicel and peduncle AZs. In particular, the compositions of the present invention include novel nucleic acid molecules, including recombinant DNA molecules, cloned genes or degenerate variants thereof, especially variants occurring naturally, which encode JOINTLESS gene products. The nucleic acid sequence of the tomato JOINTLESS gene (also referred to as 240K4.12) is also provided.
The compositions of the present invention further include cloning vectors, including expression vectors, containing the nucleic acid molecules of the present invention, and hosts transformed with the nucleic acid molecules of the present invention. The present invention also contemplates methods for identifying and isolating genes homologous to the JOINTLESS gene in plants other than tomato.
Other aspects of the present invention include expression vectors designed to express the protein coded for by the JOINTLESS gene, plant lines transformed to carry the JOINTLESS gene, host cells transformed to express proteins encoded by JOINTLESS gene, and antibodies specifically reactive to those proteins.